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Instrument: CERES-PFM : Clouds and the Earth's Radiant Energy System - Prototype Flight Model
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The Cloud's and the Earth's Radiant Energy System (CERES) is a 3-channel radiometer measuring reflected solar radiation in the 0.3-5 µm wavelength band, emitted terrestrial radiation in the 8-12 µm band, and total radiation from 0.3 µm to beyond 100 µm. These data are being used to measure the Earth's total thermal radiation budget, and, in combination with MODIS data, detailed information about clouds. The first CERES instrument was launched on the Tropical Rainfall Measuring Mission (TRMM) satellite in November 1997 as CERES-PFM; the second and third CERES instuments were launched on the Terra satellite in December 1999 as CERES-FM1 AND -FM2; and the fourth and fifth CERES instruments are on board the Aqua satellite, as CERES-FM3 and CERES-FM4.

CERES consists of two broadband scanning radiometers that measure the Earth's radiation balance and provide cloud property estimates to assess their role in radiative fluxes from the surface to the top of the atmosphere.

CERES is a broadband scanning thermistor bolometer package with extremely high radiometric measurement precision and accuracy. The Terra spacecraft carries two identical instruments: one operates in a cross-track scan mode and the other in a biaxial scan mode. The CERES Terra cross-track scanning data greatly extends the CERES data from the Tropical Rainfall Measuring Mission (TRMM) to achieve complete global measurements by adding mid-latitude and polar observations. TRMM data is restricted by its orbit to roughly cover 40S to 40N. Terra crosstrack data also adds observations at different times of day than TRMM (and later Aqua) in order to increase the accuracy of measuring the large diurnal cycle of the radiation fields from day to night. Finally, the CERES Terra biaxial scan mode provides new observations of the angular radiation fields in order to greatly improve the accuracy of the final fluxes of solar and thermal energy used to derive the Earth's radiation balance.

Each CERES instrument has three channels - a short-wave channel for measuring reflected sunlight, a longwave channel for measuring Earth-emitted thermal radiation in the 8-12 µm "window" region, and a total channel for total radiation. Onboard calibration hardware includes a solar diffuser, a tungsten lamp system with a stability monitor, and a pair of blackbody sources. Cold space and internal calibration looks are performed during each normal Earth scan.

CERES is a Principal Investigator instrument provided by NASA and managed by NASA's Langley Research Center (LaRC) in Hampton, Virginia. The instrument was built by TRW in Redondo Beach, California. The CERES Team Leader is Norman Loeb.

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Instrument Owner: USA/NASA

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